SEMICONDUCTOR FREQUENCY STANDARD BASED ON P(16) SPECTRAL LINE OF ACETYLENE ISOTOPE WITH TEMPERATURE STABILIZATION BY PHASE MODULATION

This paper reviews the method of semiconductor laser diode frequency stabilization by phase modulation. Also parameters are identified that affect the quality of stabilization and the estimation of Allan deviation is obtained. The pilot setup has been put together and it consists of: a semiconductor distributed feedback laser diode, a fiber phase modulator, an electrical signal generator, an acetylene-13 isotope cuvette, a photodetector, a lock-in amplifier and personal computer for measurement processing. Modulated laser diode radiation passed through a gas cell provides information about the position of radiation spectral line relative to the center of gas spectral line. Gas molecular spectral lines provide frequency standard with low sensitivity to external effects. When using the reference signal, one can get an error signal in a lock-in amplifier that changes the laser diode temperature and, as a result, its wavelength. Allan deviation was estimated based on measured frequency data. Long-term stability can be improved in the time range between 0.1 s and 100 s up to 1∙10-8 (Allan deviation). This method of stabilization is useful for the development of compact high reliable optical frequency standards for space applications.